1. Field of the Invention
The present invention pertains to advancing material of indeterminate length through an arcuate guide on a cushion of pressurized air. The arcuate guide floatingly suspends a running web on a cushion of air without contacting the guide.
2. Background Information
The invention pertains to contactless turning guides for a running web and for guiding and controlling a running web through a change of direction. These turning guides are also commonly referred to as air rolls or air turns and are formed as a partial drum-like member having an arcuately curved surface which can be variable as to its transverse length and also variable as to the length of its arc. These prior art turning guides have a transverse nozzle slot at both the beginning and end of the arcuate path for supplying pressurized air to the air cushion located therebetween. Generally the prior art devices do not have a steering device to prevent the web from lateral side-to-side motion, and instead the running web weaves uncontrollably back and forth in a transverse direction. This is referred to as "web weave" and sometimes becomes so severe that the web may rub against the machine frame members, and tear, thereby causing a shut down of the machine for re-webbing. In modern printing presses, web weave caused by guideless air turns is one of the major causes for lost production time.
One prior art contactless turning guide is shown in U.S. Pat. No. 4,197,972 which issued Apr. 15, 1980 to Robert A. Daane, one of the inventors in this present application. Other prior art examples are shown in the U.S. Pat. No. 4,182,472, issued on Jan. 8, 1980 and U.S. Pat. No. 4,282,998, issued Aug. 11, 1981, both issued to Peekna.